Factors Influencing The Air Permeability Of The Nonwoven Air Filter

Effect of fabric weight

Fabric weight which is generally measured in gm/m2 play an important role in the performance of non woven filter fabric The air permeability decreases with the increase in fabric weight due to the number of fibres per unit area. Also due to increase in fabric density the resistance to air flow increases. Due to increase in fabric weight the pressure drop increases thus improving the filtration efficiency. The tenacity at break increases with the fabric weight in both bias and cross direction. This is due to the increase in no. of fibres in the web, leading to increase in no. of vertical loops and density and entanglement. Thus, causing less freedom of fibre movement and greater frictional resistance. But the breaking elongation decreases gradually in both bias and cross direction with the increase in fabric weight.

Effect of fabric density and thickness

The air permeability decreases non-linearly as thickness or fabric density increases. The density has a more significant influence on air permeability than either thickness or fibre size. There can be no general correlation between porosity and permeability because the permeability of a material is influenced by the capillary pressure curves. Air resistance increased with fabric thickness and fabric weight per unit area, but decreased with fibre fineness.